1. Field of the Invention
The present invention relates to a bearing metal positioning structure in a split connecting rod, particularly to a bearing metal positioning structure with low production costs and improved accuracy of positioning the bearing metal.
2. Background Art
In general, a bearing metal composed of a pair of bearing metal halves, each of which is formed into a 180 circular-arc shape in cross-section, is inserted in a large-diameter end portion of a split connecting rod for an internal combustion engine. An oil film is formed between the bearing metal and a crank pin to lubricate between the connecting rod and the crank pin.
The pair of bearing metal halves are mounted between a rod side upper half and a cap side lower half of the large-diameter end portion while being positioned so as not to move in the peripheral direction and in the axial direction.
To effect the positioning of the bearing metal halves, in general, a projection is formed at one of both the peripheral ends of each bearing metal half formed into a 180 circular-arc in cross-section. As shown in FIG. 11 of this application, locking grooves 05b and 05a are formed in the inner peripheral surfaces, on the mating plane sides, of upper and lower halves of the large-diameter end portion of the split connecting rod, respectively. The positioning of the bearing metal halves is performed by engaging the projections in the locking grooves 05b and 05a (see Japanese Patent Publication No. Hei 2-19328, and Japanese Patent Laid-open No. Sho 61262219).
FIG. 11 is a schematic partial view, seen from the inner peripheral surface 01d side, of large-diameter end portion 01a of a split connecting rod. In FIG. 11, reference numeral 02 designates an upper half of the large-diameter end portion, and 03 is a lower half (cap side half) of the large-diameter end portion. The inner peripheral surface 01d forms a bearing hole for rotatably supporting a crank pin.
In the above method, however, because the halves 02 and 03 of the large-diameter end portion 01a of the split connecting rod are separately machined to form the locking grooves 05b and 05a in the inner peripheral surfaces, on the mating plane sides, of the upper and lower halves 02 and 03, production costs are raised.
When the split connecting rod is configured as the breaking-split connecting rod, an integrally die-formed body is broken along a breaking plane C. The die-formed body is formed into the rod side half containing the upper half 02 of the large-diameter end portion 1a, and a cap side half being the same as the lower half 03 of the large diameter end portion 1a.
The rod side half and the cap side half are assembled into one body, and the locking grooves are mechanically finished in the assembled state. In this case, only the paired locking grooves opposed and communicated to each other with the breaking plane C can be mechanically finished. The locking grooves 05b and 05a located on the opposed sides with respect to the breaking plane C at different axial positions cannot be mechanically finished.
To mechanically finish the locking grooves 05b and 05a, the locking groove 05b of the rod side half and the locking groove 05a of the cap side half must be separately, mechanically finished before assembly of the rod side half and the cap side half into one body. This likely results in damage to the breaking plane C during machining.
Further, if the split connecting rod is configured as a breaking-split type connecting rod, the breaking plane C of an integrally die-formed body becomes bearing metal locking planes 017b and 017a in the circumferential direction of the locking grooves 05b and 05a, which degrades the accuracy of positioning the bearing metal.
An object of the present invention is to solve the above-described problems of the related art bearing metal positioning structure in a split connecting rod, and to provide a bearing metal positioning structure in a split connecting rod with reduced production costs by eliminating the necessity of machining locking grooves on the split connecting rod side, and improving the accuracy of positioning the bearing metal.
Another object of the present invention is to provide a bearing metal positioning structure in a split connecting rod which is less likely to involve error in assembling the bearing metal in the split connecting rod.